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Vauxhall VXR8 Bathurst S
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Discussion Starter #1
Took some video for reference a while ago before fitting a taller 5th gear set into my Tremec TR6060 manual box.
The issue I have is the car is supposed to redline at around 166 in 5th - and shifting into 6th at that speed is useless because 6th will just bog down. This is an issue as you hit the redline in 5th around 100yards before the standing mile marker - so you end up crossing the line bouncing off the limiter.
So I was after a cheap and effective way to ensure I was still accelerating over the the line.
If My calculations are correct, I should be able to pull 185+ in 5th.

So the "before" runs: First, determine the rev cut in 4th:


and then see where we hit the wall in 5th (this was a lot more gentle):


So the theory is sound, new 5th gear has been fitted, next video when I get back from an Airfield in a few weeks.
 

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Excessive speed kills...no need for it, all that truly matters is 0-60 times and if u live in a city, who will get to the next light the quickest.....
 

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Premium Member
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Maybe taller tires? The gear should really help though... I've hit 168mph in 5th (6-speed auto with 3.45 Camaro gears) and still had a few hundred RPM before redline (I chickened-out... but was driving on salt). My math (26.7in diameter tires) would put me at 184mph in 5th at 6800rpm.

-Todd...
 

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Vauxhall VXR8 Bathurst S
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179 Posts
Discussion Starter #5
Cheers- I did consider a set of taller tyres and even a different diff - but that would compromise the overall gearing throughout - this way I keep the acceleration throughout (with no discernable slack in 5th...so far) and the cruising 6th gear. It also means that if I ever was able to redline in 5th and pull 6th, it should, in theory keep accelerating (however slowly)

The 5th gearset fitted actually worked cheaper than a new set of taller tyres too :D
 

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HeapBlaster
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442 Posts
my speedo said 160 on the nose when i was in 5th and I think i was at 5500rpm... stock TR6060 stock 3.70 gear and a 245/40R19 Michelin.

also, why not just bump your limiter up? at that speed the extra shift is time you could be in the gas and you're covering ground very quickly... i cant imagine it pulling another 500 rpm or so in 100yrds... a set of good double valve springs and a 7200rpm limiter
 

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Vauxhall VXR8 Bathurst S
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179 Posts
Discussion Starter #9
my speedo said 160 on the nose when i was in 5th and I think i was at 5500rpm... stock TR6060 stock 3.70 gear and a 245/40R19 Michelin.

also, why not just bump your limiter up? at that speed the extra shift is time you could be in the gas and you're covering ground very quickly... i cant imagine it pulling another 500 rpm or so in 100yrds... a set of good double valve springs and a 7200rpm limiter

The charger is out of steam by the low 6 k's - so really the aim was just to ensure I was accelerating in 5th all the way through the mile marker
 

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Excessive speed kills...no need for it, all that truly matters is 0-60 times and if u live in a city, who will get to the next light the quickest.....
0-06 is all that matters? yeah that gets you real far on the 1/4 mile, standing mile, and open roads like the autobahn (the latter 2 he mentioned directly)

unless we start racing 100 yards, there will always be more important things than 0-60times
 

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Car RamRod
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1,795 Posts
Excessive speed kills...no need for it, all that truly matters is 0-60 times and if u live in a city, who will get to the next light the quickest.....
I get your point. And that was the motto for the 55mph national speed limit. But your 0-60 is all that matters statement? Most folks here measure performance on the dyno or the 1/4 mile. 0-60 matters to Motor trend...this is not the "motor trend" crowd.
 
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